Carburetor



Patented Nov. 8, 1938 UNITED STATES PATENT OFFICE 2,135,539 CARBURETOR. John B. Sinderson, Rockford, Ill. Application April 27, 1936, Serial No. 76,569

Claims. This invention relates to carburetors, and has for its principal object the provision of a car-- buretor which does not rely upon the impingement of inrushing air upon a spray nozzle to produce the mixture, but which has an air metering valve mechanically connected with a fuel metering valve so that any movement of the one results in a proportionate movement of the other, thereby definitely insuring a mixture of predetermined proportions at every point throughout the range of operation.

An important feature of my improved carburetor is the provision of a bellows responsive to reductionin pressure in the carburetor casing to move a perforated air metering valve ring relative to a conical head, whereby to vary the section of the throat between the ring and head and accordingly vary the amount of air admitted for the combustible mixture.

Another important feature is the provision of a novel form of fuel metering valve comprising a slotted plunger which in its endwise movement uncovers more and more of the slot therein and accordingly varies the amount of fuel supplied. This plunger by virtue of another novel feature has a double seal against fuel leakage in its closed position.

The invention is illustrated in the accompanying drawing, in which Figure -1 is a central longitudinal section through a carburetor embodying my invention;

Fig. 2 is anenlarged sectional detail of the fuel valve portion of Fig. 1;

Fig.3 is a cross-section on line 3-3 of Fig. 2;

Fig. 4 is a fragmentarysectional view illustrating a modified or alternative construction;

Fig. 5 is a side view of an air metering head of' modified form, and

Figs. 6 and 7 are fragmentary views showing different forms of fuel metering slots for'the fuel valve.

The same reference numerals are applied to corresponding parts throughout the views.

As indicated above, the carburetor of my invention does not rely for its mixture upon the impingement of air upon a spray nozzle. It is well known in .this art that the cross-section of the .air' inlet and the bore of the spray nozzle can be proportioned to give a mixture of exactly right proportionsat any one suction in the throat of the carburetor, but atall other suctions the proportions of the mixture will be wrong. The carburetor herein disclosed is so constructed that for every degree of opening of the air valve, the fuel valve issimultaneously opened to the correct position to insure a mixture of predetermined proportions at every point throughout the range of operation. While I at present prefer that the mixture be constant through the full range, it will soon appear from the description of my construction that I can readily arrange to provide for a leaner mixture with increasing manifold pressure, and thus obtain maximum economy.

Referring first particularly to Fig. 1, 5 is the usual butterfly throttle valve in the outlet passage 6, the extent of opening of which determines the amount of fuel mixture passing to the engine. Fuel is discharged at 1 onto the cone 8 which may be either a hollow metal member with numerous small holes provided therein, or else, as herein shown, a cone of fine screen or foraminous material, so that the air can flow through the apertures or interstices and form a combustible mixture with the fuel discharged onto the cone. At 9 is a frusto-conical head having a cylindrical portion Ii] on which a valve ring H has a close working fit. i2 is a collapsible and expansible bellows supported on the plate l3 clamped to the casing M of the carburetor by the small housing I5 fastened suitably by screws l6 to the casing. The housing l5 encloses the bellows l2 and has air inlet openings [1 in the end wall thereof shown covered by the ring I l, the latter being in closed position. The end wall of housing I5 also provides a support for the head 9 which is threaded in place, as indicated at i8. A yoke l9 spans the head 9 and is attached to the ring ll so as to transmit movement to the rod 20 when the ring H rises and falls with the collapsing and expanding of the bellows. When a reduction in pressure is created in the casing M by the turning over of the engine, the intake manifold of which communicates with the outlet passage 6, as indicated at 2|, air rushes in between the conical surface of the head 9 and the inner circumference of the ring II, when the latter has raised past the cylindrical portion l0. Obviously, the higher the ring H is raised the greater the volume of air admitted. At wide open throttle, enough air will be admitted through the ring H to make a properly proportioned mixture with the fuel discharged at 1 onto the cone 8. The ring H, in other words, is an apertured piston member movable up and down in the casing substantially without air leakage around it, and is movable under atmospheric pressure in response to reduction in pressure in the casing.

The fuel discharge port 1 is in the bottom of a housing 22 supported on and projecting into the carburetor casing Hi and secured with its cover 23 to the casing suitably by screws 24. The housing 22 provides a float chamber 25 therein communicating through a tube 26 with a source of fuel supply which may be either a vacuum tank delivering fuel by gravity to the float chamber, in the usual way, or a fuel pump driven by the engine. The float 21 operates the valve 28 to shut off communication between the tube 25 and the float chamber when fuel is approximately at the level indicated, above the intake end of the fuel passage 29 leading to an outlet 3! Fuel is delivered from the outlet 33 to the discharge port 1 in regulated amounts, as hereinafter appears, depending upon the position of the fuel metering valve 3| which is operated by a rod 32. Now, the rods 2|] and 32 have racks 33 and 34, respectively, meshing with a gear 35 mounted for rotation on a shaft 36 suitably supported in the casing l4. A yoke 31 fas: tened to the inside of the casing M, as shown,

provides guides in two planes at right angles to one another for the racks 33 and 34 to maintain these racks in proper meshing engagement with the gears 35. This yoke also provides an abutment for a light coiled compression spring 38 which surrounds a portion of the rod 20 and engages the yokes l9 and 31 at opposite ends. This spring serves to return the interconnected parts to the position illustrated, namely, with the air metering valve ring H and fuel metering valve 3| in closed position.

The operation of the carburetor, as thus far described, is as follows: When the throttle valve is opened and the engine is turned over in the usual way for starting, a reduction in pressure is created in the casing M of the carburetor. Atmospheric pressure acting upon the ring therefore starts the collapse of the bellows l2, and the ring rises off the cylindrical portion i] of the head 9 and admits air through the annular space between the ring and the conical portion of the head. Now, of course, the ring will stabilize itself at a certain level where the volume of air taken in balances or satisfies the suction delivers a proportionate amount of fuel through the port 1 onto the cone 8 for mixture with. the air passing through the cone, whereby to furnish a correctly proportioned mixture to the engine.

The proportioning of fuel and air, as will soon appear, may be either constant throughout the range of operation or varied so as to become leaner with increasing manifold pressure, as dis' tinguished from the simple spraying type of carburetor which enriches the mixture with increasing manifold pressure and consequent increasing air speeds through the'throat. Obviously, more economical operation is insured if the mixture becomes somewhat leaner as the manifold pressure increases. With the carburetor of my invention, it is a simple matter to that the fuel valve can be given the same lineal movement as the air valve H, as shown in Fig. or else the reduction gearing shown at 35 in Fig. 4 may be employed wherein the rack 33 operates on the portion of large diameter of the gear element 35 and the rack operates on the portion of small diameter.

On the other hand, if the mixture is to become leaner with increasing manifold pressure, I may do either one of two things to accomplish this result: I may either varyv the inletof air so as to feed more air 'in proportion tofuel with increased manifold pressure, or I may vary the feeding of fuel so as to deliver less fuel with increased manifold pressure. The differential air feed is'obtainable by simply providing a head 9', as shown in Fig. 5, in place of the conical head 9 shown in Fig. 1. The convex'form of the surface of the head 9','especially in the region of the cylindrical base portion [3, will obviously cut down the amount of air delivered in'relation to the amount of fuel under low manifold pressure conditions, although under increased manifold pressure conditions, enoughadditional air will be supplied in relation'to the fuel delivery,

to provide aleaner mixture. Obviously, since the air control head can be .unthreaded at l3, it is.

a simple matter to substitute a head of the desired shape to obtainwhatever operating characteristicsare desired. In Fig. 7 Ihave shown a fuel metering slot 39 in a valve 3|, which, because of its narrowing down toward the right hand end, will provide for less fuel delivery in relation to air with increased manifold pressure and accordingly result in a leaner mixture. It is obviously a very simple matter to substitute one valve for another in the present construe- 7 tion, inasmuch as the valve 3| has a sliding fit. 1

Hence, one may readily obtain whatever operat: ing characteristics are desired. It is important to note that in the operation of my carburetor the full area of the ring II is subject toatmospheric pressure at alltimes whereby to move the ring according to the reduction in pressure in the casing and thereby operate the valve 3| proportionately. In other words, there is assurance of the desired amount of power and the desired length of movement of the ring H required in metering the air and fuel. 7

Referring to Figs. 2 and 3, the valve 3| isenclosed in a bushing 40 suitably entered with a press flt in the bore 4| in the bottom of the housing 22. A hole 42 in one end of the'bushing establishes communication between the passage 29 in the housing22 and the L-shaped outlet passage in a plug 43 entered with a press fit'in the end of the bushing 40. A fiat is milled lengthwise of the bottom of the bushing to provide a fuel outlet passage communicating at one and at its other end with another port 46 provided in the wall of the bushing. Now, a sleeve 41 entered with a press'flt in the bushing .43

provides a bearing wherein'the valve 3| is arranged to operate with a close working fit. The latter comprises a cylindrical body 48 forming a continuation of the rod 32, which is milled off lengthwise from its inner end, as at 49, to the point to provide a fuel passage 5|. Two sleeves; 52 and 53 are secured onto the body 48 either with'apress fit or by sweat-soldering, and between these two sleeves a split sleeve 54 is secured to the body 48 suitably by sweat-soldering. The

two halves of;the sleeve 54. are machined very.

accurately along the longitudinal edges to provide an accurate metering slot 39 or 39', as the ,case may be, before the two halves are placed on the body 48. Obviously, it is a simple matter with this construction to obtain a very accurately measured slot 39 or 39, because in the fastening of the two halves, of the sleeve 54 to the body 48, a ffeeler of the exact thickness of the slot desired can be entered between the edges where the slot is to be, while the halves are being sweatsoldered in place. Then, after that, the resulting assembly can be machined or ground, and lapped, if necessary, to bring it to the exact outside diameter desired so as to fit closely in the bore .of the sleeve 41. The slot 39 obviously communicates with the. passage A hole 55 in the sleeve 52 communicates with the passage 5| so that fuel from the outlet 30 can find its way into the passage 5| .and then through the slot 39 to the port 45 when the valve 3| is opened by movement to theleft from the position illustrated in Fig. 2. The amount of overlapping shown at 56 corresponds in its lineal'dimension to the amount of movement required of the air valve ll before air is delivered into the casing l4. In other words, the 'fuel delivery commences at the same time with the air delivery. The small collars shown at 51 and 58 on opposite sides of the port 46 have a close working fit on the valve, and in case any fuel finds its way through the bushing 51, the port 46 will drain such fuel from between the bushings 5l-and 58, so that no fuel will drip inside the casing 14 from the end of the bushing 49. The projecting inturned end of the sleeve 52 forms a holder for a rubber ball 59 which is pressed against the plug 43 when the valve 3| is closed, thus tightly sealing the fuel outlet 39 to prevent leakage. There is in fact a double seal when the ball 59 is seated at 39, because of the overlap at 56, previously referred to. This eliminates any danger of fuel dripping and going to waste when the engine is standing idle. ,The rubber material employed for this packing member 59 will be of special composition not subject to deterioration by contact with the fuel, such materials being at present available, as is well known.

In conclusion, attention is called to the flap 60 pivoted at 5! and held closed under pressure of the torsion spring 62 sealing the opening 63 in the end of the carburetor casing I 4. This flap valve is merely a safeguard for the bellows l2 to prevent any injury thereto in the event of a back-fire. Obviously this valve 68 will remain closed and prevent leakage of air during normal operation when there is a reduction in pressure in the casing-but will open instantly in the event of a back-fire, whereby to relieve the pressure.

While I have shown the plate I I movable relative to the head 9, it is of course evident that the arrangement might be reversed, in which event the plate would be rigid with the casing and the head movable with one end of the bellows and reversed end for end from the position shown. In like manner, while I have disclosed a slotted fuel metering plunger movable in a bushing, it will be evident that this arrangement might also be reversed and the movement be given to the part surrounding a fixed slotted part to uncover different lengths of slot for the same purpose. Then too, while the accelerator pedal would in accordance with the present disclosure be connected to operate the throttle valve, an operative structure would result if the throttle valve were omitted and the accelerator pedal connected to either the air valve H or fuel valve 3|.

It is believed the foregoing description conveys a good understanding of the objects and advantages of my invention. The appended claims have been drawn with a view to covering all legitimate modifications and adaptations.

I claim:

1. A carburetor comprising a casing having an outlet passage for conducting combustible mixture to an engine, a throttle valve therein, a tapered air metering head, an apertured air metering valve plate wherein said head fits to form a closure, said head and plate elements being relatively movable to provide therebetween a variable air inlet opening for said casing, the movable element being movable inwardly relative to said casing under atmospheric pressure, a bellows interposed between said element and said casing, and means for delivering liquid fuel for mixture in said casing with the air admitted through said inlet.

2. A carburetor comprising a casing having an outlet opening for conducting combustible mixture to an engine, means for delivering air in metered amounts to said casing to mix with fuel, comprising a tapered air metering head, an apertured air metering valve plate wherein said head fits to form a closure, said head and plate elements being relatively movable to provide therebetween a variable air inlet opening for said casing, the movable element being movable inwardly relative to said casing under atmospheric pressure, and a. bellows interposed between said element and said casing, a metering valve for delivering fuel in metered amounts to said casing to mix with the air, and means interconnecting said metering valve and the movable element of the aforesaid air metering means.

3. In a carburetor, a casing closed except for an outlet opening to communicate with the intake manifold of an engine, an air inlet valve on a wall of said casing arranged to open under atmospheric pressure when a reduction in pressure is created in said casing by said engine, whereby to supply air to said casing in proportion to said pressure reduction, the valve comprising an air metering valve head and an air metering valve plate apertured to receive the head, one of said parts being movable under atmospheric. pressure in response to reduction in pressure in the casing to admit a regulated amount of air, and a fuel valve so constructed and operatively connected with the movable member of said air valve to supply fuel to said casing in predetermined proportion to the air for mixture with the air in the casing.

4. In a carburetor, a casing, a fuel metering valve discharging therein comprising a tubular guide, a hollow plunger recip-rocable in said guide and having a longitudinally extending slot pro:- vided in the wall thereof, a fuel supply chamber at one end of said guide, the same having a fuel supply port in alignment with said plunger to which liquid fuel is delivered under substantially constant pressure, said plunger projecting into said chamber and having constant communication therewith throughout its range of endwise movement, whereby the fuel discharged from said plunger is metered according to the length of slot uncovered at the other end of the guide when the plunger is moved endwise relative to the guide, and a closure for said fuel supply port on the adjacent end of said plunger, and means for delivering air in proportionate amounts for mixture in said casing with the fuel discharged from the fuel metering valve.

5. A structure as set forth in claim 4, wherein the parts are so arranged that the end of the slot is inwardly spaced a predetermined distance from the end of the guide when the supply port is closed -by the closure, whereby to provide a double seal against fuel leakage.

6. In acarburetor, a casing closed except for an outlet opening to communicate with the intake manifold of an engine, a suction operated air intake valve on said casing, the valve comprising a stationary air metering valve head and a relatively movable air metering valve plate apertured to receive the head and movable under atmospheric pressure in response to reduction in pressure in the casing, a fuel metering valve connected with the movable air valve plate and arranged to be opened to an extent determined by the'opening of the air valve, and a throttle valve in the outlet opening independent of any connection with the air and fuel valves.

"7. In a carburetor comp-rising a casing, an air metering valve comprising a stationary tapered head on said casing, and an apertured valve plate wherein said head fits to form a closure therefor, said valve plate being movable in said casing as a piston substantially without air leakage between the plate and casing whereby to provide a variable sized air inlet opening between the plate aperture and said head for the inlet of a variable amount of air to said casing, said head being of a predetermined shape in relation to the range of movement of the plate whereby to afford predetermined variation in the area of opening between the plate and head in different positions of the plate relative to thehead, and means for delivering liquid fuel for mixture in said casing with the air admitted by said air metering valve. 8. In a carburetor comprising a casing, an air metering valve comprising a stationary tapered head on said casing, an apertured valve plate wherein said head fits to form a closure therefor, said valve plate being movable in said casing as a piston substantially without air leakage between the plate and casing whereby to' provide a variable sized air inlet opening between the plate aperture and said head for the inlet of a variable amount of air to said casing, said head being of a predetermined shape in relation to the range of movement of the plate whereby to afford predetermined variation in the area of opening between the plate and head in different positions of the plate relative to the head, a metering valve for delivering fuel in metered amounts to said casing to mix with the air, and means interconnecting said fuel metering valve and the air valve plate.

9. A structure as set forth in claim 7, wherein said head is removable from said casing independently of said plate, whereby to permit sub stitution of a different shaped head affording a different variation in the area of opening between the plate and head in corresponding positions of the plate relative to the head.

10. A structure as set forth in claim 7, wherein the aperture in the plate is round and the head is circular in cross-section and disposed in concentric relation to saidaperture, and wherein said head is threadedly mounted in'said casing for removal thereof independently of said plate.

11. A structure as set forth in claim 7, wherein the head is of uniform cross-section at the base thereof throughout a predetermined range of initial movement of said plate, the aperture in the plate receiving said uniform base portion with a'close working fit.

12. A structure as set forth in claim 7, wherein said head is of cylindrical form at the base thereof throughout a predetermined range of initial movement of said plate, the aperture in the plate being round and receiving said cylindrical portion with a close working fit, and wherein said head is threadedly mounted in said casing for removal thereof independently of said plate. i

13; In a carburetor, a casing, a fuel metering valve discharging therein comp-rising a tubular element, and a hollow rod element fitting therein with a close working fit, the rod element having a longitudinally extending slot provided in the wall thereof, the rod having liquid fuel delivered thereto under substantially constant pressure, said rod and tube elements being arranged to have relative endwise movement, and the discharge of fuel being metered according to the length of slot uncovered at the end of the tubular element, and means for delivering air in proportionate amounts for mixture in said casing with the fuel discharged from the fuel metering valve.

14. A structure as set forth in claim 13 wherein the rod element comp-rises an inner substantially cylindrical body having a longitudinal recess formed on one side thereof, and a sleeve split lengthwise and fitting on said body, the two sleeve sections having opposed longitudinal edges disposed in spaced relation to form the longitudinal metering slot adjacent the longitudinal recess, the recess constituting a fuel passage. V

15. In a carburetor, a casing, a fuel metering valve discharging therein comprising a' tubular element, a hollow rod element fittingrtherein with a close working fit, the rod element having a longitudinally extending slot provided in the wall thereof, said rod and tube elements being arranged to have relative endwise movement,

and the discharge of fuel being metered according to the length of slot uncoveredrat the end of the tubular element, means providing a fuel supply chamber at one end of said rod element, the same having a fuel supply portin alignment with the rod element to which liquid fuel is delivered under substantially constantpressure, the rod projecting into said chamber and having constant communication therewith throughout 'its range of endwise movement, and a closure for said fuel supply port carried on the end of said rod, and means for delivering air in proportionate amounts for mixture in said casing with the fuel discharged from the fuel metering valve. 7

JOHN B. SINDERSON. 

